Fix the code that causes warnings

core/fxge/win32/fx_win32_gdipext.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "core/fxge/include/fx_ge.h"
 
 #if _FX_OS_ == _FX_WIN32_DESKTOP_ || _FX_OS_ == _FX_WIN64_DESKTOP_
 #include <windows.h>
@@ skipping 655 matching lines @@
   }
   Point destinationPoints[] = {Point(dest_left, dest_top),
                                Point(dest_left + dest_width, dest_top),
                                Point(dest_left, dest_top + dest_height)};
   CallFunc(GdipDrawImagePointsI)(pGraphics, bitmap, destinationPoints, 3);
   CallFunc(GdipDisposeImage)(bitmap);
 }
 CGdiplusExt::CGdiplusExt() {
   m_hModule = NULL;
   m_GdiModule = NULL;
-  for (int i = 0; i < sizeof g_GdipFuncNames / sizeof(LPCSTR); i++) {
+  for (size_t i = 0; i < sizeof g_GdipFuncNames / sizeof(LPCSTR); i++) {
     m_Functions[i] = NULL;
   }
   m_pGdiAddFontMemResourceEx = NULL;
   m_pGdiRemoveFontMemResourseEx = NULL;
 }
 void CGdiplusExt::Load() {
   CFX_ByteString strPlusPath = "";
   FX_CHAR buf[MAX_PATH];
   GetSystemDirectoryA(buf, MAX_PATH);
   strPlusPath += buf;
   strPlusPath += "\\";
   strPlusPath += "GDIPLUS.DLL";
   m_hModule = LoadLibraryA(strPlusPath.c_str());
   if (!m_hModule) {
     return;
   }
-  for (int i = 0; i < sizeof g_GdipFuncNames / sizeof(LPCSTR); i++) {
+  for (size_t i = 0; i < sizeof g_GdipFuncNames / sizeof(LPCSTR); i++) {
     m_Functions[i] = GetProcAddress(m_hModule, g_GdipFuncNames[i]);
     if (!m_Functions[i]) {
       m_hModule = NULL;
       return;
     }
   }
   uintptr_t gdiplusToken;
   GdiplusStartupInput gdiplusStartupInput;
   ((FuncType_GdiplusStartup)m_Functions[FuncId_GdiplusStartup])(
       &gdiplusToken, &gdiplusStartupInput, NULL);
@@ skipping 805 matching lines @@
                    dest_pitch);
     }
   }
   CFX_DIBitmap* pDIBitmap = _FX_WindowsDIB_LoadFromBuf(
       pInfo->pbmi, pData, pInfo->pbmi->bmiHeader.biBitCount == 32);
   FX_Free(pData);
   FreeDIBitmap(pInfo);
   return pDIBitmap;
 }
 #endif